Modelling Ancient Earth Climate: Methods & Models Prof. Alan M. Haywood School of Earth & Environment, University of Leeds, Leeds, LS2 9JT. with contributions from Paul Valdes, Ulrich Salzmann, Victoria Peck, Steve Hunter & Jane Francis

Why? Understand the dynamics of warm climatesUnderstand the dynamics of warm climates Test Earth System ModelsTest Earth System Models

Simulation of the historical or near-historical record Simulation of the historical or near-historical record Analysis of the observed record of variability Analysis of the observed record of variability Projection for the next 100 years Projection for the next 100 years Primary Research Focus in Climate Change Science Greatest Strengths Spatial and temporal character of the Observations. Measurement of physical quantities that define the state of the atmosphere and ocean. Greatest Weaknesses Sense of change. Sense of the integration of the Earth System.

Greatest Strengths Spectacular sense of change (Furry Alligator Syndrome) True integrated system response Greatest Weaknesses Proxies rather than state variables Limited spatial and temporal resolution In contrast: A Research Focus in Earth History “The greatest weaknesses in a research focus on the modern record are the greatest strengths of Earth System History”

We Should Worry IPCC Climate Sensitivity: IPCC Climate Sensitivity: Roughly 1.5 to 4.5 C globally averaged surface temperature increase for a doubling of carbon dioxide. Hundreds of GCM experiments have been completed for time periods throughout the Phanerozic using a wide variety of climate models. Many experiments focused on either glacial climates or warm climates (the extremes). “There is no legitimate example of a climate model simulation in which the past climate conditions were overestimated” in which the past climate conditions were overestimated”

ClimateHistory

Atmospheric carbon dioxide through the Phanerozoic and projected into the next century. Inset modified from figure constructed by S. Porter (2003). L. Sohl constructed the Phanerozoic portion (2003).

The Climate System

General Circulation Models Model needs to simulate albedo, emissivity and general circulation. Use “first principles” Newton's Laws of Motion 1 st Law of Thermodynamics Conservation of Mass and Moisture Hydrostatic Balance Ideal Gas Law

Spectrum of Climate Models Energy Balance Models (EBM’s) Atmospheric General Circulation Models (AGCM) AGCM + Slab Ocean Model Coupled Ocean Atmosphere GCM (OAGCM) EMIC ESM Number Complexity

Components of an Earth System Model Aerosols: Dust and Sulphates Aerosols: Regional Model: High Resolution Regional Model: High Resolution Cryosphere- Lithosphere Model Model AtmosphericChemistryAtmosphericChemistry Atmospheric General Circulation Model Land Surface Hydrology Hydrology Ocean General Circulation Model Ocean Carbon Cycle Ocean Carbon Cycle Terrestrial Carbon Cycle Cycle

Brief history of numerical modelling

ATMOSPHERE LAND OCEANICESULPHUR CARBONCHEMISTRY ATMOSPHERE LAND OCEANICESULPHUR CARBON ATMOSPHERE LAND OCEANICESULPHUR ATMOSPHERE LAND OCEANICE ATMOSPHERE LAND OCEAN ATMOSPHERE LAND ATMOSPHERE Development of Met. Office Climate Models Component models are constructed off-line and coupled in to the climate model when sufficiently developed 1960s Present 1990

Physical basis of climate models The atmosphere is a fluid on a rotating planet: –Drag at the surface and within the atmosphere affects the momentum budget –Water vapour evaporates from the surface, condenses to form clouds and heats the atmosphere when it is lost through precipitation –Heating from solar radiation and cooling from thermal radiation Models therefore need to include equations for; –3 components of wind (or vorticity & divergence), including Coriolis and drag –equation of state and conservation of water –thermodynamics, including heating by condensation and radiation

The ocean is also a fluid, but incompressible. It is heated by solar radiation and cooled by evaporation and thermal emission from the surface. No internal heating, but salinity strongly affects the density and hence the circulation The ocean is also a fluid, but incompressible. It is heated by solar radiation and cooled by evaporation and thermal emission from the surface. No internal heating, but salinity strongly affects the density and hence the circulation Additional models have been developed to include the land surface, cryosphere, atmospheric chemistry and aerosols, carbon cycle etc Additional models have been developed to include the land surface, cryosphere, atmospheric chemistry and aerosols, carbon cycle etc Processes that are sub-grid in scale are modelled by parametrizations Processes that are sub-grid in scale are modelled by parametrizations Physical basis of climate models

HadCM3 GCM 20 Ocean Levels 19 Atmospheric Levels Atmospheric resolution: 3.75 by 2.5 degrees Ocean resolution :1.25 by 1.25

19 levels in atmosphere 20 levels in ocean 2.5 lat 3.75 long 1.25 THE HADLEY CENTRE THIRD COUPLED MODEL - HadCM3 no flux adjustments 30km -5km

Parametrized processes in the ECMWF model

Representation of orography; the importance of resolution The upper figure shows the surface orography over North America at a resolution of 480km, as in a low resolution climate model. The lower figure shows the same field at a resolution of 60km, as in a weather forecasting model. Remember that orographic processes are highly non- linear.

The horizontal and vertical resolutions of climate models need to be high enough to avoid numerical errors and to resolve the basic dynamical and transport processes There is a trade-off between resolution and computing time, but model resolutions are increasing continually, as more computer power becomes available So………

Ice Sheet Elevation From Peltier, 1994 Temperature Change BiomesPrecipitation

CaseStudies 1. Palaeo ENSO (El Niño Southern Oscillation) Coupled ocean-atmosphere phenomena Involves large scale fluctuations in a number of oceanic/atmospheric variables (e.g. sea surface temps. & sea level pressure) El Niño & La Niña opposite extremes of ENSO

The Pliocene: a Permanent El Niño-like state? (Wara et al., 2005; Philander & Federov, 2003) Mg/Ca SSTs 05 Age (Ma) 3 Strong Gradient No Gradient

Difference between Pliocene Control and Pre-Ind (  C) Plio Control ocean temperatures (  C) across the Pacific at 0  N Can a model reproduce this change?

ENSO rather than permanent El-Niño! Haywood et al. (in-press). Paleoceanography

“In search of palaeo-ENSO: significance of changes in the mean state” 1 sample per 10,000 years

Mid Holocene ENSO - Palaeo Data

Additional Modelling Experiments Ocean Gateways Ocean Gateways Trace Gas Concentrations Trace Gas Concentrations Altered Model Parameters Altered Model Parameters

CaseStudies 2. Ice-Sheet Initiation (E/O boundary) E/O boundary Marine  18 0 Antarctic ice- rafted detritus PalaeobotanicalEvidence Zachos et al. (2001)

PalaeocenePresent Antarctica: from Greenhouse to Ice-house

Causal Mechanisms for Antarctic Ice-Sheet Initiation Ocean Gateways Ocean Gateways Antarctic elevation Antarctic elevation Declining atmospheric CO 2 concentrations Declining atmospheric CO 2 concentrations

Important Gateways Evolution of major ocean gateways since the Eocene. During the last 50 million years (Ma) subtropical gateways (blue bars) closed and high latitude gateways (red bars) opened. (Figure courtesy of Bill Hay, GEOMAR).

GCM - Climatologies DeConto & Pollard, 2003.

Ice-sheet Model

DeConto & Pollard, X CO 2 3 X CO 2 Ice-sheet Model

DeConto & Pollard, Sensitivity Tests

InitialModelling

CaseStudies 3. Cretaceous Climates & Ice-Sheets PalaeobotanicalEvidence Cretaceous forest 120 million years ago on the Antarctic Peninsula. reconstruction based on PhD of Jodie Howe, University of Leeds/BAS, painted by Robert Nichols.

Evidence for large, rapid sea-level changes (Miller et al., 2005) Evidence for eustatic nature Pace and magnitude suggest glacial origin. Suggest moderate-sized ice sheets ( × 10 6 km 3 ). Paced by Milankovitch forcing. CO 2 levels through the Maastrichtian 2 greenhouse episodes ppm But suggestions of CO 2 low-points at ~70 and 66 Ma. (Nordt et al., 2003; Beerling et al., 2002).

How to create a Maastrictian model Change solar output~0.6% less than present CO 2 (and other gases)4 x pre-industrial (but could be 2x to 8x. Volcanic activityAssume same as today. Change in orbitSame as present, but perform sensitivity simulations PalaeogeographyIncluding sea-level/ orography/ bathymetry/land ice Previous modelling also required prescription of vegetation, and sea surface temperatures (or ocean heat transport) but this is no longer needed.

Maastrictian Orography At climate model resolution. Original palaeogeographies from Paul Markwick

Coupled Ocean-Atmosphere Simulation: Comparison to Oxygen Isotopes Paul Pearson's Maastrictian data Model predicted temperatures approx. 10C at 1000m, 8C at 2000m, and 7C at 3000m c.f. temperatures from 14C to 7C from D’Hondt & Arthur (2002)

Coupled Ocean-Atmosphere Simulation: Comparison to Vertebrate Data Paul Markwick's database Red squares= all crocs, Orange= Dinosaurs, White = Other Vertebrates Model predicted cold month mean shown by 5C contour (red) and 0C (blue)

2xCO 2 - ~ 2 x 10 6 km 3 ice Suite of HadCM3 derived palaeoclimatesSuite of HadCM3 derived palaeoclimates –2, 4, and 6 x CO 2 –Further runs being carried out including 1 x CO 2 Comparison against climate proxy databaseComparison against climate proxy database Climate then used to drive a BAS ice-sheet model.Climate then used to drive a BAS ice-sheet model. 2xCO 2 4xCO 2 + favourable orbit Ice Sheets in a Greenhouse World

The Future: Data & Models Combine Limiting Factors: Available computer power Model sophistication (resolution etc.) Small community (“every department needs a pet modeller”) Language barriers & a lack of communication A new generation of scientists to act as the interface A couple of examples what modellers need from the geological community Ocean temperatures Land cover “Deep-time perspectives on climate change: marrying the signal from computer models and biological proxies (Eds. M. Williams, A. M. Haywood, J. Gregory and D. Schmidt) The Micropalaeontological Society & the Geological Society of London”

Oceans: Quantitative temperature estimates derived from multi-proxy studies PRISM & MARGO H. Dowsett (in-press). Kucera et al. (2005) QSR Vol. 24,

New 3-D Ocean Temperature Reconstructions: multiple equilibrium?

Land Cover: Vegetation and Biomes derived from paleobotanical studies ProxiesBiomesData Translation and Reconstruction  Nearest Living Relatives  Plant functional types  Full Biomisation Fossil Leaves Pollen Fossil Wood Rainforest Grassland Savanna

PLIOCENE BIOMES: DATA–MODEL COMPARISON Paleo-Data Biomes Model Biomes

Summary Glaciation in a Greenhouse word? Glaciation in a Greenhouse word? Importance of ACC on EAIS kick off? Importance of ACC on EAIS kick off? Permanent El-Niño? Permanent El-Niño? How its Done How its Done Need for Integration Need for Integration Why Model? Why Model? NO PROBLEM